1. Field of the Invention
The present invention relates to a water treatment system; and more particularly relates to a water treatment system for a vessel.
2. Brief Description of Related Art
In general, some problems associated with ballast water treatment include the following:
The use of UV, Ozone and Electro Chemical type treatment systems have limiting factors by way of the size and power consumption of the plant.
The major segment of the BWTS market is the refit portion where existing machinery space and the necessary extra generating power are not readily available (all ship types).
New builds can of course have the extra space and power required by these systems to be designed in.
Currently, treatment is undertaken during ballast operation in port at high flow rates with the inherent risk of non-compliance by having only one main treatment plant—should the plant fail or water quality is worse than the plant is able to disinfect.
With cargo operations being undertaken simultaneously, this is the most stressful time for a ship's crew to be looking after an additional complex system.
By way of example, current known and available treatment technologies utilize “in-line” treatment and bulk chemical additive:
In-Line.
In-line treatment systems are in-variable coupled into the existing ship's ballast pumping systems and suffer from at least one of the following problems:                (1) Variation to the existing designed ballasting flow rate due to additional piping restrictions.        (2) Variation to flow rate due to additional components being added, e.g., UV, Ozone, and Electro Chemical reactors/injection systems.        (3) The problems encountered with systems requiring additional filtration (reduction in flow—required pressure differential for backwash, downtime due to backwash cycles).        (4) The systems are required to treat/disinfect at the same potentially high flow rates of the ship's existing ballast pumps which offers potential problems of fast changing water quality conditions (e.g. sediment may pass through filters) and change in water quality due to flotation levels of the ship (ballasting in tidal waters).        (5) Due to the varying water qualities and flow rate, disinfection techniques are not able to vary the required treatment dosing levels instantaneously to achieve compliant disinfection levels.        (6) Some treatment systems due to the by-products produced and lack of control due to flow rate may incur other associated problems (e.g., corrosion due to uncontrolled PH levels and/or high levels of unrequired toxicity).        (7) The electrical power requirements of existing disinfection systems treating very high flow rates can be prohibitive to fitting to all types of ships (especially retro-fit where existing generating capacity may be a limiting factor).        
Chemical Addition.
These systems require an amount of disinfection chemicals to be added to the tank based on water volume (not on water quality). The invention is constantly monitoring disinfection levels and actual living cell count within the water to add chemicals to an absolute minimum to achieve compliant disinfection levels. Chemical addition is not normally by a recirculating method (recirculating increases mixing/dispersal within the tank for more effective).
In view of this, there is a need in the industry to enhance the current available treatment technologies that utilize the aforementioned “in-line” treatment and bulk chemical additive.
In particular, techniques for ship ballast sterilization are known in the art. By way of example, some known techniques are summarized below:
For example, U.S. Pat. No. 7,025,889 (see FIG. 7 in the '889 patent) discloses a technique for recirculation in a ballast water treatment system, consistent with that described in column 5, lines 14 through 21, which is hereby incorporated by reference in its entirety. The '889 patent does not disclose the use of an in-line VF to control the output of the UV lamp.
Further, United States Patent Publication no. US2010/0116647 discloses a ballast water treatment plant having a filter, disinfection, instrumentation and control unit, which is also hereby incorporated by reference in its entirety.
Furthermore, U.S. Pat. No. 6,773,611 discloses techniques for controlling organisms in ballast water, which is also hereby incorporated by reference in its entirety. The technique in the '611 patent is based at least partly on a chlorine dioxide biocide based system, and does not disclose the use of VF to determine the number of living organisms.
In view of this, there is a need in the industry for solutions to problems encountered in operating the system, e.g., fouling of the lamps or VF.
Moreover, the implementation of new ballast water treatment and discharge regulations by the United States Coast Guard (USCG) in 2013 and pending International Maritime Organization (IMO) regulations has created a demand of a monitoring system that can provide information on the discharge quality in real time or near real time and can be easily integrated and operating by ship technicians and engineers. There are a variety of such monitoring systems on the market or in development but none address the challenges of an ever changing water matrix that can contain a variety of interfering substances and conditions.
In view of this, there is also a need in the industry for a new technique to address the most challenging conditions that can negatively impact the variable fluorescence data quality. This need is particularly important in relation to, e.g., a ballast discharge application, due to the potentially expensive and time consuming consequences of inaccurate discharge data creating a false positive or false negative result.